The present invention is related to motors and, in particular, to reducing the temperature variations experienced by a rotor of a motor.
In many different applications, a motor or other machine that includes a rotor that can be placed in systems where it experiences a wide range of temperatures. For example, an induction motor can be used to drive an impeller that draws air through a heat exchanger in an aircraft. The combination of the motor and the impeller is sometimes referred to as a ram air fan. While the aircraft is on the ground, outside air is drawn by the ram air fan through the heat exchanger. The air is used to carry heat away from the heat exchanger. Internal portions of the ram air fan are cooled by cooling air that is diverted around the heat exchanger. When the aircraft is in flight, the cooling air is significantly colder than when it is on the ground. As such, the internal portions of the motor (e.g., the rotor) can experience wide-ranging temperature cycles that can result in shortened lifecycles for the rotor.